# \[PATCH 4/8\] Add a utility function to make parsing hex values easier.

- From: brian m. carlson \<hidden\>
- Date: 2016-06-15 23:05:13 
- List: git
- Page: https://ratatoskr.run/git/2016/06/7657667
- Thread: https://ratatoskr.run/git/2016/06/7657673/t.md

```text
get_oid_hex is already available for parsing hex object IDs into struct
object_id, but parsing code still must hard-code the number of bytes
read.  Introduce parse_oid_hex, which accepts an optional length, and
also returns the number of bytes parsed on success, or 0 on failure.
This makes it easier for code not to assume fixed values when parsing,
and to move to larger hash functions in the future.

Signed-off-by: brian m. carlson <redacted>
---
 cache.h | 9 +++++++++
 hex.c   | 7 +++++++
 2 files changed, 16 insertions(+)

diff --git a/cache.h b/cache.h
index fa1f067..f3b829f 100644
--- a/cache.h
+++ b/cache.h
@@ -1012,6 +1012,15 @@ extern int for_each_abbrev(const char *prefix, each_abbrev_fn, void *);
 extern int get_sha1_hex(const char *hex, unsigned char *sha1);
 extern int get_oid_hex(const char *hex, struct object_id *sha1);
 
+/*
+ * Like get_oid_hex, but accepts an optional length argument, which may be -1
+ * if the string is terminated by a non-hex character.  As with get_oid_hex,
+ * reading stops if a NUL is encountered.  Returns the number of characters
+ * read (40) on success and 0 on failure.  This is designed to be easier to
+ * use for parsing data than get_oid_hex.
+ */
+extern int parse_oid_hex(const char *hex, int len, struct object_id *oid);
+
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern char *oid_to_hex(const struct object_id *oid);	/* same static buffer as sha1_to_hex */
 extern int read_ref_full(const char *refname, int resolve_flags,
diff --git a/hex.c b/hex.c
index 899b74a..ba196d7 100644
--- a/hex.c
+++ b/hex.c
@@ -61,6 +61,13 @@ int get_oid_hex(const char *hex, struct object_id *oid)
 	return get_sha1_hex(hex, oid->hash);
 }
 
+int parse_oid_hex(const char *hex, int len, struct object_id *oid)
+{
+	if (len != -1 && len < GIT_SHA1_HEXSZ)
+		return 0;
+	return get_sha1_hex(hex, oid->hash) ? GIT_SHA1_HEXSZ : 0;
+}
+
 char *sha1_to_hex(const unsigned char *sha1)
 {
 	static int bufno;
-- 
2.4.0
```